A police news release late Wednesday said the six officers were indefinitely suspended, which is equivalent to termination under civil service rules.

Three other officers initially suspected of wrongdoing resigned when an investigation was launched into the ticket-writing scandal in March.

The department identified the officers fired Wednesday only by their first initials. They are R. Peoples, P. Aguilar, J. Dunn, M. Middleton, M. Mosqueda, and R. Wigginton.

In April, the FBI joined the investigation into whether the officers violated federal law. Some of the overtime was paid with federal grant money.

No charges have been filed.

Agents collected boxes of tickets and other evidence at the department's traffic unit, where the officers were assigned, police said in a news release at the time.

The officers were suspected of deliberately omitting the time on otherwise legitimate tickets they wrote, then filling in the time later to make it appear they worked overtime, police spokesman Lt. Paul Henderson said in April.

The investigation started when a supervisor noticed discrepancies in the ticket book of an officer who had gone on leave, Henderson said.

"The fate of all nine now rests in the hands of the judicial system," Halstead said Wednesday in a written statement. "Maintaining public safety while maintaining the public's trust is a crucial component of our relationship with the community we serve. Integrity matters and I will always safeguard the public's trust by aggressively investigating allegations of misconduct and taking decisive action."

Halstead announced earlier he had suspended all overtime under the grant program, which is called the Selective Traffic Enforcement Program, or STEP.

Agents from the inspector general's office of the U.S. Department of Transportation are also investigating.